@Aleksandr Ivanov do you have more details? Does your backend receive an empty body or does it respond with an empty body?

In all cases, I would recommend setting up a Charles proxy to capture the traffic

Previously I sent wrong information. The request body from iOS build is not empty. Experimented with charles. On android (successful response):

:method: POST
:path: /graphql
:scheme: https

content-type: application/json; charset=utf-8
content-length: 316
accept-encoding: gzip
user-agent: okhttp/4.5.0
pragma: no-cache
cache-control: no-cache

{"operationName":"DriverSchedulePageQuery","variables":{"filter":{"from":"2020-10-15","to":"2020-10-29"}},"query":"query DriverSchedulePageQuery($filter: DateFilter!) { driverSchedule(filter: $filter) { __typename content { __typename date duties { __typename id driverShiftId type startAt endAt } } totalPages } }"}

on iOS (400 response):

POST /graphql HTTP/1.1

Content-Type: application/x-www-form-urlencoded
User-Agent: Driver%20App/140 CFNetwork/1197 Darwin/19.6.0
Connection: keep-alive
Accept: */*
Accept-Language: en-us
Content-Length: 316
Accept-Encoding: gzip, deflate, br

{"operationName":"DriverSchedulePageQuery","variables":{"filter":{"from":"2020-10-15","to":"2020-10-29"}},"query":"query DriverSchedulePageQuery($filter: DateFilter!) { driverSchedule(filter: $filter) { __typename content { __typename date duties { __typename id driverShiftId type startAt endAt } } totalPages } }"}

The main difference I see is

Content-Type

Yes the problem was in the Content-Type. I manually set

content-type: application/json; charset=utf-8

and it works. Thank you for advice to use Charles 👍

I don't think OkHttp does anything by default, we are doing it: https://github.com/apollographql/apollo-android/blob/62673dc817967725bfcadc2ceb1bed3b503e82da/apollo-runtime-kotlin/src/jvmMain/kotlin/com/apollographql/apollo/network/http/ApolloHttpNetworkTransport.kt#L169

@Aleksandr Ivanov do you mind opening an issue, we should do the same for iOS

(Also I don't really want to depend on ktor for a simple use case like this)

@mbonnin https://github.com/apollographql/apollo-android/issues/2665